Objective: To explore the source of small supernumerary marker chromosome in a case.
Methods: G-banded karyotyping, fluorescence in situ hybridization, multiple sequence tagged sites (STS) of the Y chromosome, and Illumima Human Cyto SNP-12 Beadchip analysis were carried out.
Results: The karyotype was mos 46,X,+mar1[21]/46,X,+mar2[78]. Y chromosome STS analysis has displayed the presence of sy84, sY86, USP9Y and DDX3Y genes from the AZFa region, and sY1227 of the AZFb region, while sY1228, sY1015, sY127, sY134 from the AZFb region, and sY254 and sY255 from the AZFc region were missing. FISH analysis has verified both of the marker chromosomes to be Y chromosome fragments. Mar1 was ish.idic(Y)(q11.2)(SRY++,DXZ1+,DYZ3++,DYZ1-), while mar2 was ish.del(Y)(q11.2)(SRY+,DXZ1+,DYZ3+,DYZ1-). Single nucleotide polymorphism (SNP) microarray analysis showed that the Yq11.2-Yq12 has lost a 10.81 Mb fragment.
Conclusion: The marker chromosomes were verified to be aberrant Y chromosomes, with the breakage and recombination occurring in Yq11.2. Mar 1 was an isodicentric Y chromosome (idic(Y)pter to q11.2::q11.2 to pter), and mar2 was del(Y)(q11.2). The karyotype was mos 46,X,ish idic(Y)(q11.2)(DYZ3++,SRY++,DXZ1+,DYZ1-)[21]/46,X,ish del(Y)(q11.2)(DYZ3+,SRY+,DXZ1+,DYZ1-)[78]. Combined FISH, Y chromosome STS analysis, SNP microarray analysis and other technologies can facilitate determination of the nature of marker chromosomes.